Coating machine and electrode panel therefor



P 1, 1953 L. w. SPOONER 2,650,565

COATING MACHINE AND ELECTRODE PANEL THEREFOR Filed Dec. 50, 1949 "Fig.1.

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I r I Ifiventor: Laurence W. Spooner,

,His Attfney.

i atented Sept. 1, 1953 COATING MACHINE AND ELECTRODE PANEL THEREFORLaurence W. Spooner, Pittsfield, Mass., assignor to General ElectricCompany, a corporation of New York Application December 30, 1949, SerialNo. 136,120

3 Claims.

My invention relates to a machine for coating sheet material withcomminuted material in an electrostatic field to produce felt and hasfor its object the provision of low corona electrodes for use in such amachine.

Another object of my invention is to provide electrodes encased in anionization-free medium.

Machines of this character include a pair of spaced electrodes betweenwhich a strip of a base material and a portion of .an endless belt aresimultaneously moved in the same direction within the machine. Theunderside of the base material strip is covered with an adhesivematerial. The belt portion continually carries fibers from the outlet ofa hopper mounted upon the machine into position between the electrodeswhich are energized to provide an electrostatic force therebetween. Thefibers are attracted to the adhesive surface of the base there to becomeperpendicularly attached by means of the adhesive material, to form afelt strip. This method of attaching particles to an adhesive surface isalso used in the manufacture of abrasive papers and cloths to cause theparticles of abrasive to stick with their long axes perpendicular to thebases so that sharp cutting points project from the surfaces of thefinished products.

For effective operation of such a machine, the distance betweenelectrodes is less than three inches with an applied voltage of from 60to 100 kilovolts. In order to accommodate the moving strip and themoving belt, a minimum distance of one-half inch between electrodes isrequired. The machine with bare electrodes has been operated in achlorinated gas atmosphere to raise the dielectric breakdown value, buteven then it was found that corona formed around the electrodes of themachine at a voltage gradient too low to attract the particles to thebase strip efi'ectively. It was found, in addition, that corona voltagevaries substantially directly with the distance between electrodeswithin /3 to three inches spacing and that coronafrequently starts at avoltage but slightly less than the arc-over or puncture voltage betweenelectrodes. After operation of the machine over a period, corona wasfound to have burned the insulation of the machine excessively.

According to my invention, the metal electrodes formerly used in thismachine are replaced by electrode panels each comprising a sheet ofconducting material inserted within insulation material and compressedso that the conducting material is enclosed in an ionization-freemedium. The panels are mounted in the machine with the conductinmaterial connected by leads to a source of power to form the electrodesof the machine. It was found that the corona starting voltage for amachine in which the electrode panels were installed to replace bareelectrodes was nearly tripled.

An object of my invention is to provide electrode panels embodying thesefeatures.

Another object of my invention is to provide electrode panels to raisethe corona starting voltage of the machine.

A further object of my invention is to provide electrode panels, eachcomprising a flat sheet of conductive material wholly embedded in apanel between laminated sheets of insulation material.

A still further object of my invention is to provide electrodes enclosedin an insulating material so that upon installation of such electrodesthere can be no ionizable atmosphere adjacent thereto.

For a better understanding of my invention, reference is directed to theaccompanying drawing of one embodiment of my invention in which Fig. 1is a schematic view of a felt coating machine embodying my invention;Fig. 2 is a sectional view of an electrode panel mounted in the coatingmachine.

Referring to the drawing, a coating machine I is provided with panels 2enclosing electrodes 3, one of which is connected by a lead 4 to agrounded source of direct current power and the other of whichiselectrically grounded at 4A, to provide an electrostatic field betweenpanels 2.

A strip 5 of material to form the base of the felt being produced by themachine is moved in the direction of arrow 6 from supply reel I and iswound upon reel 8 by motor means (not shown). The under surface of strip5 is coated with an adhesive material. An idler pulley 9 and a drivepulley l0 operate to drive a continuous belt in the direction of arrow 6at the same speed that strip 5 moves. The upper portion of the beltbetween pulleys 9 and I0 extends beneath strip 5 and a storage hopper l2mounted so as to be capable of receiving fiber from outside the machine.

As the machine is operated, fibers from hopper l2 drop on belt portionII and thereby are carried between electrode panels 2 to be attracted bythe force of the electrostatic field therebetween to the under surfaceof strip 5. The fibers meet strip 5 in a position perpendicular to thesurface thereof and are held in this position by the adhesive materialthereon.

Electrode panels 2 are constructed by piling sheets of insulation l3together to form a stack.

A sheet of semi-conducting material 3 and a substantially two inchsquare sheet I l of copper foil in electrical contact with sheet 3 andsubstantially centered thereon, are inserted between the insulatingsheets. Conductin sheet 3 is positioned in the stack so as to be atleast one-half inch from the edges of the panel. The stack is pressed atsubstantially 1,500 pounds per square inch pressure at 160 C., for onehour, after which it is cooled and removed from the press. A hole I5 isa carefully drilled in the panel with a blunt drill to expose copperfoil 14. The copper foil is tinned and the hole is filled with solder I6to provide an adequate means of electrical connection.

An electrode spacing of 1% inches is arbitrarily chosen within the abovementioned one-half inch and three inch electrode spacing limits of themachine. Each electrode 3 is a semi-conductor comprising a sheet ofinsulating material impregnated with semi-conducting paint and dried.

It was found that corona starting voltage of the electrode panels in anatmosphere of air is substantially 280% of the corona starting voltageof bare metal electrodes having the same spacing.

While certain specific. embodiments have been shown and described, itwill, of course, be understood that various modifications may be madewithout departing from the invention. The appended claims are,therefore, intended to cover any such modifications within the truespirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electrode comprising a flat sheet of conducting material, a flatsheet of semi-conducting material substantially larger than said sheetof conducting material lying thereon in contact therewith and extendingover the edges thereof, an insulating member completely enclosing saidsheets, and an electrical lead connected to said sheet of conductingmaterial at the approximate center thereof on the side opposite thecontact area between said sheets and extending without said insulatingmember along a line substantially perpendicular to the surfaceof saidsheets.

2. In a machine for coating an adhesive covered surface of sheetmaterial with comminuted material, a pair of electrode panels, eachpanel comprising a flat sheet of conducting material, a flat sheet ofsemi-conducing material substantially larger than said sheet ofconducting material in contact therewith, substantially centered thereonand extending over the edges thereof, a plurality of sheets ofinsulating material, each substantially larger than said sheet ofsemi-conducting material, said sheet of conducting material and saidsheet of semi-conducting material being sandwiched between said sheetsof insulating material and completely enclosed thereby, and anelectrical lead connected to said sheet of conducting material at theapproximate center thereof on the side opposite the contact area betweensaid sheets and extending without said insulating member along a linesubstantially perpendicular to said sheet, said panels being arranged inparallel planes and being positioned in said planes so that the sheetsof conducting material have the semiconducting layers interposedtherebetween, whereby the corona starting voltage between the electrodepanels is greatly increased.

'3. A machine for coating an adhesive covered surface of sheet materialwith comminuted material, comprising a hopper for storing comminutedmaterial mounted at one end of said machine, driving means forconducting said sheet material in a horizontal strip within saidmachine, said strip being conducted with said adhesive surface facingdownward, driven endless belt surface, said belt means serving to conveysaid comminuted material from said hopper to a position beneath saidsurface, and a pair of similar laminated electrode panels, one of saidelectrode panels being mounted above said sheet material and the otherof said electrode panels being mounted below said endless belt, each ofaid electrode panels including a flat sheet of conducting material, aflat sheet of semi-conducting material substantially larger than saidsheet of conducting material in contact therewith, sub-stantiallycentered thereon and extending over the edges thereof, a plurality ofsheets of insulating material, each substantially larger than said sheetof semi-conducting material, said sheet of conducting material and saidsheet of semi-conducting material being sandwiched between said sheetsof insulating material and completely en closed thereby and anelectrical lead connected to said sheet of conducting material at theapproximate center thereof on the side opposite the contact area betweensaid sheets and extending without said insulating member along a linesubstantially perpendicular to said sheet, said panels being arranged inparallel planes and being positioned in said planes so that the sheetsof conducting material have the semi-conducting layers interposedtherebetween, whereby the corona starting voltage between the electrodepanels is greatly increased.

LAURENCE W. SPOON-ER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,572,937 Kempton Feb. 16, 1926 2,128,817 Hawley Aug. 30, 19382,165,738 Van Hoffen July 11, 1939 2,187,624 Melton et al Jan. 16, 19402,416,280 Bennett Feb. 25, 1947 2,439,859 Muller Apr. 20, 1948 2,449,356Wilkoff Sept. 14, 1948 2,492,404 Streib et a1. Dec. 27, 1949

